Method and apparatus for aligning a laser to a waveguide

ABSTRACT

An apparatus includes a slider structure having a waveguide and a cavity configured to align a laser to the waveguide. The cavity includes a plurality of solder bumps on a bottom of the cavity configured to electrically and thermally couple the laser to the slider. At least one mechanical stopper is disposed in the cavity to facilitate vertical alignment between an output of the laser and an input of the waveguide. At least one solder bump is disposed on the mechanical stopper to facilitate lateral alignment between the output of the laser and the input of the waveguide in response to a reflow of the solder bumps.

SUMMARY

Various embodiments described herein are generally directed to methods,systems, and apparatuses that facilitate aligning a laser to a waveguideon a slider structure. In one embodiment, an apparatus comprises a laserand a slider including a waveguide and a cavity configured to align thelaser to the waveguide. The cavity includes a plurality of solder bumpson a bottom of the cavity configured to electrically and thermallycouple the laser to the slider. At least one mechanical stopper isdisposed in the cavity to facilitate vertical alignment between anoutput of the laser and an input of the waveguide. At least one solderbump is disposed on the mechanical stopper to facilitate lateralalignment between the output of the laser and the input of the waveguidein response to a reflow of the solder bumps.

In another embodiment, an apparatus comprises a laser and a sliderincluding a waveguide and a cavity configured to align the laser to thewaveguide. The cavity includes a first plurality of solder bumps on abottom of the cavity configured to electrically couple the laser to theslider, and a second plurality of solder bumps disposed on the firstplurality of solder bumps. The second plurality of solder bumps has alower melting point than the first plurality of solder bumps. A reflowof the second plurality of solder bumps facilitates lateral alignment ofan output of the laser to an input of the waveguide. At least onemechanical stopper is disposed in the cavity to facilitate verticalalignment of the output of the laser to the input of the waveguide inresponse to a reflow of the first and second plurality of solder bumps.

In another embodiment, a method for aligning a laser to a waveguide on aslider involves forming a cavity on a slider including a waveguide. Thecavity comprises at least one mechanical stopper, a first plurality ofsolder bumps, and at least one second solder bump. The laser ispositioned on at least the second solder bump. The slider is reflowed toalign an output of the laser to an input of the waveguide. The firstplurality of solder bumps facilitates a vertical alignment between thecavity and the laser during the reflow, and the second solder bumpfacilitates a lateral alignment between the cavity and the laser duringthe reflow.

These and other features and aspects of various embodiments may beunderstood in view of the following detailed discussion and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The discussion below makes reference to the following figures, whereinthe same reference number may be used to identify the similar/samecomponent in multiple figures.

FIGS. 1A-1C are cross-sectional views of a laser and a slider includinga waveguide and a cavity configured to align the laser to the waveguideaccording to an example embodiment;

FIGS. 2A-2C are top views of a laser and a slider including a waveguideand a cavity configured to align the laser to the waveguide according toan example embodiment;

FIGS. 3A-3C are cross-sectional views of a laser and a slider includinga waveguide and a cavity configured to align the laser to the waveguideaccording to another example embodiment;

FIGS. 4A-4D are cross-sectional views of a laser and a slider includinga waveguide and a cavity configured to align the laser to the waveguideaccording to various embodiments;

FIG. 5 illustrates various processes for aligning a laser to a waveguideon a slider in accordance with various embodiments; and

FIGS. 6-7 show various processes for aligning a laser to a waveguide ona slider in accordance with other embodiments.

In the figures, like reference numerals may be used to designate likeelements.

DETAILED DESCRIPTION

The present disclosure is generally directed to recording heads used inmagnetic recording devices such as hard drives. In particular, thisdisclosure relates to heat assisted magnetic recording (HAMR), which isone technique used to increase areal data density of magnetic media.HAMR generally refers to the concept of temporarily and locally heatinga recording media to reduce the coercivity of the media so that anapplied magnetic writing field can more easily direct the magnetizationof the media during the temporary magnetic softening of the media causedby the heat source. A tightly confined, high power laser light spot canbe used to heat a portion of the recording media. Then the heatedportion is subjected to a magnetic field that sets the direction ofmagnetization of the heated portion. This approach to magnetic recordingmay also be referred to by other names, as thermal assisted magneticrecording (TAMR). Also, similar approaches may be used in other types ofdata recording, such as in magneto-optical (MO) systems.

In a HAMR device, optical guiding and focusing elements may beintegrated in a recording head (also referred to as a “slider”) tocouple the output of a laser light to the recording location and confinethe laser light to a small spot on the media. One method of couplinglaser light into these optical elements is to include a laser on therecording head itself and direct the laser output into an input of awaveguide on the recording head. The waveguide transmits the light to alocation adjacent to an air bearing surface (ABS) of the slider, andfrom this location the light is directed to the recording media.

Active alignment can be used to achieve the alignment between the laserand the waveguide. Active alignment involves positioning the laserproximate to the waveguide with the laser output on and monitoring thecoupled laser power while moving the laser to final position, afterwhich the laser is attached (e.g., soldered) in place. Active alignmentmay be prohibitively expensive for mass production of hard drives andother devices. An alternative to active alignment is passive alignmentmethod, which involves alignment and attachment with the laser off. Inthe embodiments, discussed below, apparatuses and methods are describedto facilitate accurate passive alignment of a laser with aslider-integrated waveguide.

In the disclosed embodiments, a mechanical stopper may be deployed in acavity of the slider to facilitate vertical alignment between the laserand the waveguide. But friction or adhesion on the mechanical stoppermay create shear forces that prevent proper lateral alignment. Theembodiments described below include features that provide increasedcoupling efficiency by improving the three dimensional alignment of thelaser to the waveguide. The benefits for improving the alignment includebetter slider yield and higher reliability of the laser. HAMR writingrequires a certain minimum amount of light to reach the ABS. Installinga poorly aligned laser would result in the recording head to bescrapped. Better alignment allows lasers to run at lower current therebyimproving laser reliability.

FIGS. 1A-1C are cross-sectional views of a laser and a slider includinga waveguide and a cavity configured to align the laser to the waveguideaccording to an example embodiment. Referring to FIG. 1A, the slider 100includes a waveguide 102, and a cavity 120. A laser 110 includes a laserlight channel 112, and is positioned in the cavity 120 to align anoutput 112B of the laser light channel 112 into an input facet 102A ofthe waveguide 102. The cavity 120 includes a plurality of solder bumps122 on a bottom 120D of the cavity 120 configured to electrically andthermally couple the laser 110 to the slider 100. The cavity 120 furtherincludes at least one mechanical stopper 124 disposed in the cavity 120that facilitates vertical alignment between the output 112B of the laserand the input facet 102A of the waveguide 102.

The cavity 120 further includes at least one solder bump 126 disposed onthe mechanical stopper 124, wherein the at least one solder bump 126facilitates lateral alignment between the output 112B of the laser lightchannel 112 and the input facet 102A of the waveguide 102 in response toa reflow of the solder bumps 122 and 126. The material of solder bumps122 may or may not be same as the material of solder bump 126. Underbump metallization (UBM) 128 is disposed under the at least one solderbump 126 and under the solder bumps 122. The UBM 128 is configured toprovide a strong, low-stress mechanical and electrical connectionbetween the solder bumps 122 and the mechanical stopper 124. The UBM 128can also limit the diffusion of solder bumps 126 and 122 into theunderlying material and prevent oxidation of the underlying material.Additionally, the UBM 128 limits the lateral movement of the solderbumps 126 and 122 during reflow. The laser 110 further includes lasercontacts 114 configured to contact the solder bumps 122.

As illustrated in FIG. 1A, the laser 110 is positioned in the cavity120, on top of the plurality of solder bumps 122. During a reflow of thesolder bumps 122 and 126, the mechanical stoppers 124 facilitatevertical (Z direction) alignment between the output 112B of the laser110 and the waveguide input facet 102A, as shown in FIG. 1B. Inaccordance with FIG. 1C, at least one solder bump 126 disposed on themechanical stopper 124 facilitates lateral (X and Y directions)alignment between the output 112B of the laser 110 and the waveguideinput facet 102A by reducing friction on the mechanical stopper 124, inresponse to the reflow. The shear modulus drops close to zero onmaterials above the melting temperature during reflow. A surface tensionof the plurality 126 of solder bumps provides lateral alignment betweenthe output 112B of the laser 110 and the waveguide input facet 102A inresponse to the reflow. The mechanical stoppers 124 serve as Z-stop.According to various embodiments, the mechanical stoppers 124 compriseat least one member that does not electrically couple the laser 110 tothe slider 100 after the reflow of the solder bumps. According tovarious embodiments, the laser output 112B is aligned with the waveguideinput facet 102A using passive alignment, without turning on the laser.

FIGS. 2A-2C are top views of a laser and a slider including a waveguideand a cavity configured to align the laser to the waveguide according tovarious embodiments. FIG. 2A shows a top view of the embodiment inaccordance with FIG. 1A, FIG. 2B shows a top view of the embodiment inaccordance with FIG. 1B, and FIG. 2C shows a top view of the embodimentin accordance with FIG. 1C. In FIGS. 1A-1C and 2A-2C, like referencenumerals designate like elements. Dashed lines in FIGS. 1A-1C and 2A-2Crefer to the portions of elements cannot be seen from the correspondingdirection in reality.

FIG. 2A shows that the laser 110 is not aligned with the waveguide 102before reflow. According to various embodiments, FIG. 2B shows theslider during reflow and FIG. 2C shows the slider after reflow. Asillustrated in FIG. 2C, the output 112B of the laser light channel 112has been aligned with the input 102A of the waveguide 102 after reflow,laterally in X and Y directions. The Z direction alignment after reflowcan be better seen in FIG. 1C.

According to another example embodiment illustrated in FIGS. 3A-3C, themechanical stopper 124 comprises a non-deforming conductor 324 thatrises above the bottom 120D of the cavity 120 and electrically andthermally couples the laser 110 to the slider 100 after the reflow ofthe solder bumps 122. As shown in FIG. 3A, at least one solder bump 326is disposed on the non-deforming conductor 324, with under bumpmetallization (UBM) 328 disposed under the at least one solder bump 326and the solder bumps 122.

During reflow of solder bumps 122 and 326, FIG. 3B shows that thenon-deforming conductor 324 serves as Z-stop for vertical alignment. Thesolder bump 326 on the non-deforming conductor 324 serves multiplepurposes. First, the solder bump 326 reduces friction on thenon-deforming conductor 324 during reflow to facilitate lateralalignment in X and Y directions. Second, the solder bump 326 provideselectrical connection between the laser 110 and the slider 100 afterreflow. Furthermore, the solder bump 326 provides mechanical bonding ofthe laser 110 to the slider 100 after reflow. After the reflow, FIG. 3Cshows that the laser 110 and the slider 100 are aligned both laterallyand vertically, and are electrically and thermally coupled, as well asmechanically bonded.

According to another example embodiment, FIGS. 4A-4D are cross-sectionalviews of four steps of an alignment between a laser 110 and a waveguide102 on a slider 100. In FIG. 4A, the laser 110 and the waveguide 102 areroughly aligned prior to attach. This step can be achieved, for example,with a pick-and-place machine. As shown in FIGS. 4A-4D, the slider 100includes a cavity 120. The cavity 120 includes a first plurality 422 ofsolder bumps on a bottom 120D of the cavity configured to electricallycouple the laser 110 to the slider 100. The cavity 120 further includesa second plurality 426 of solder bumps disposed on the first plurality422 of solder bumps. UBMs 428 are disposed under the first plurality 422of solder bumps. Depending on solder materials selected, there may ormay not be UBMs between the first plurality 422 and second plurality 426of solder bumps.

According to various embodiments, the second plurality 426 of solderbumps have a lower melting point and smaller thicknesses than the firstplurality 422 of solder bumps. A reflow of the second plurality 426 ofsolder bumps facilitates lateral alignment of an output 112B of thelaser 110 to the input facet 102A of the waveguide 102. At least onemechanical stopper 124 is disposed in the cavity 120, wherein themechanical stopper 124 facilitates vertical alignment of the output 112Bof the laser 110 to the input facet 102A of the waveguide 102 inresponse to a reflow of the first 422 and second 426 plurality of solderbumps.

In FIGS. 4B and 4C, a reflow of the second plurality 426 of solder bumpsfacilitates lateral alignment of an output 112B of the laser 110 to thewaveguide input facet 102A, without a reflow of the first plurality 422of solder bumps. In FIG. 4B, the slider is heated to the lower meltingpoint of the second plurality 426 of solder bumps. Then the secondplurality 426 of solder bumps, instead of the first plurality 422 ofsolder bumps, are reflowed. Once the second plurality 426 of solderbumps have melted, surface tension forces will set lateral alignment asshown in FIG. 4C. Because the second plurality 426 of solder bumps isthin, the laser 110 will not settle onto the mechanical stopper 124. Asillustrated in FIG. 4C, the laser 110 has been laterally aligned withthe waveguide 102, after the reflow of the second plurality 426 ofsolder bumps.

In FIG. 4D, a vertical alignment between the laser 110 and the waveguide102 is achieved after a reflow of the first plurality 422 of solderbumps. The slider is heated up to the higher melting point of the firstplurality 422 of solder bumps, which causes the reflow of the firstplurality 422 of solder bumps. In response to the reflow, a surfacetension of at least the first plurality 422 of solder bumps verticallybrings the laser 110 to contact the at least one mechanical stopper 124,which facilitates vertical alignment of the output 112B of the laser 110to the waveguide input facet 102A. According to various embodiments, thelaser 110 is aligned with the waveguide 102 using passive alignment,without turning on the laser.

FIG. 5 illustrates various processes for aligning 540 a laser to awaveguide on a slider in accordance with various embodiments. The methodillustrated in FIG. 5 involves forming 510 a cavity on a sliderincluding a waveguide. The cavity comprises at least one mechanicalstopper, a first plurality of solder bumps, and at least one secondsolder bump. The method in FIG. 5 further involves positioning 520 alaser on the at least second solder bump, and reflowing 530 the slider.The first plurality of solder bumps facilitates a vertical alignmentbetween the cavity and the laser during the reflow, and the secondsolder bump facilitates a lateral alignment between the cavity and thelaser during the reflow.

FIG. 6 shows various processes for aligning 640 a laser to a waveguideon a slider in accordance with other embodiments. According to theembodiment shown in FIG. 6, after forming 610 a cavity on a sliderincluding a waveguide, the process involves forming 611 at least onemechanical stopper and forming 612 a first plurality of solder bumps ona bottom of the cavity, and forming 614 a second plurality of solderbumps on the first plurality of solder bumps. The process furtherinvolves positioning 620 a laser on a second solder bump, wherein thesecond solder bump comprises the second plurality of solder bumps havinga lower reflow temperature than the first plurality of solder bumps.According to various embodiments, the second plurality of solder bumpshas smaller thicknesses and a lower melting point than the firstplurality of solder bumps. According to various embodiments, the firstand second pluralities of solder bumps are configured to electricallyand thermally couple the laser to the slider. According to variousembodiments, the waveguide is disposed at an edge of the cavity.

The method illustrated in FIG. 6 further involves heating 632 the secondplurality of solder bumps to a lower reflow temperature, and heating 634the first plurality of solder bumps to a higher reflow temperature. Areflow of the second plurality of solder bumps facilitates to laterallyalign the laser to the waveguide, and a reflow of the first plurality ofsolder bumps facilitates to vertically align the laser to the waveguide.

According to various embodiments, the process further involves bringing636 vertically the laser to contact a mechanical stopper by a surfacetension of the first plurality of solder bumps, during the reflow.

In accordance with other embodiments, FIG. 7 shows various processes forpassively aligning 740 a laser to a waveguide on a slider. As shown inFIG. 7, after forming 610 a cavity on a slider including a waveguide,the process involves forming 712 a first plurality of solder bumps on abottom of the cavity, and forming 711 at least one mechanical stopper ona bottom of the cavity. Then, the process further involves disposing 713at least one second solder bump on the mechanical stopper. According tovarious embodiments, the mechanical stopper comprises at least onemember that does not electrically couple the laser to the slider afterthe reflow. According to various embodiments, the mechanical stoppercomprises a non-deforming conductor that rises above a bottom of thecavity and electrically and thermally couples the laser to the sliderafter the reflow. The method illustrated in FIG. 7 further involvespositioning 720 a laser on the at least second solder bump, andreflowing 730 the solder bumps on the slider.

The foregoing description of the example embodiments has been presentedfor the purposes of illustration and description. It is not intended tobe exhaustive or to limit the inventive concepts to the precise formdisclosed. Many modifications and variations are possible in light ofthe above teaching. Any or all features of the disclosed embodiments canbe applied individually or in any combination are not meant to belimiting, but purely illustrative. It is intended that the scope belimited not with this detailed description, but rather determined by theclaims appended hereto.

What is claimed is:
 1. An apparatus comprising: a slider including awaveguide and a cavity configured to align a laser to the waveguide,wherein the cavity includes: a plurality of solder bumps on a bottom ofthe cavity configured to electrically and thermally couple the laser tothe slider; at least one mechanical stopper disposed in the cavity thatfacilitates vertical alignment between an output of the laser and aninput of the waveguide; at least one under bump metallization layerdisposed on the at least one mechanical stopper; and at least one solderbump disposed on the at least one under bump metallization layer,wherein the at least one solder bump facilitates lateral alignmentbetween the output of the laser and the input of the waveguide inresponse to a reflow of the solder bumps.
 2. The apparatus of claim 1,wherein the mechanical stopper comprises at least one member that doesnot electrically couple the laser to the slider after the reflow of thesolder bumps.
 3. The apparatus of claim 1, wherein the mechanicalstopper comprises a non-deforming conductor that rises above the bottomof the cavity and electrically and thermally couples the laser to theslider after the reflow of the solder bumps.
 4. The apparatus of claim1, wherein the at least one solder bump is configured to reduce frictionbetween the laser and the mechanical stopper during the reflow.
 5. Theapparatus of claim 1, wherein the laser is aligned with the waveguideusing passive alignment.
 6. The apparatus of claim 1, wherein a surfacetension of the plurality of solder bumps provides lateral alignmentbetween the output of the laser and the input of the waveguide inresponse to the reflow.
 7. An apparatus comprising: a slider including awaveguide and a cavity configured to align a laser to the waveguide,wherein the cavity includes: a first plurality of solder bumps on abottom of the cavity configured to electrically couple the laser to theslider; a second plurality of solder bumps disposed on the firstplurality of solder bumps, wherein the second plurality of solder bumpshave a lower melting point than the first plurality of solder bumps, andwherein a reflow of the second plurality of solder bumps facilitateslateral alignment of an output of the laser to an input of thewaveguide; and at least one mechanical stopper disposed in the cavity,wherein the mechanical stopper facilitates vertical alignment of theoutput of the laser to the input of the waveguide in response to areflow of the first and second plurality of solder bumps.
 8. Theapparatus of claim 7, wherein the second plurality of solder bumps hassmaller thicknesses than the first plurality of solder bumps.
 9. Theapparatus of claim 7, wherein the laser is aligned with the waveguideusing passive alignment.
 10. The apparatus of claim 7, wherein a surfacetension of at least the first plurality of solder bumps verticallybrings the laser to contact the mechanical stopper in response to thereflow.
 11. The apparatus of claim 1, wherein a surface tension of theplurality of solder bumps vertically brings the laser to contact themechanical stopper in response to the reflow.
 12. The apparatus of claim7, wherein the mechanical stopper comprises at least one member thatdoes not electrically couple the laser to the slider after the reflow ofthe solder bumps.
 13. The apparatus of claim 7, wherein the mechanicalstopper comprises a non-deforming conductor that rises above the bottomof the cavity and electrically and thermally couples the laser to theslider after the reflow of the solder bumps.